linux-kernel - Re: [patch 1/2] mm: page_alloc: reset aging cycle with GFP

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Message-ID: <530CFEDF.3060801@redhat.com>
Date:	Tue, 25 Feb 2014 15:36:47 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Jan Stancek <jstancek@...hat.com>, Mel Gorman <mgorman@...e.de>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] mm: page_alloc: reset aging cycle with GFP_THISNODE

On 02/25/2014 03:27 PM, Johannes Weiner wrote:
> Jan Stancek reports manual page migration encountering allocation
> failures after some pages when there is still plenty of memory free,
> and bisected the problem down to 81c0a2bb515f ("mm: page_alloc: fair
> zone allocator policy").
> 
> The problem is that page migration uses GFP_THISNODE and this makes
> the page allocator bail out before entering the slowpath entirely,
> without resetting the zone round-robin batches.  A string of such
> allocations will fail long before the node's free memory is exhausted.
> 
> GFP_THISNODE is a special flag for callsites that implement their own
> clever node fallback and so no direct reclaim should be invoked.  But
> if the allocations fail, the fair allocation batches should still be
> reset, and if the node is full, it should be aged in the background.
> 
> Make GFP_THISNODE wake up kswapd and reset the zone batches, but bail
> out before entering direct reclaim to not stall the allocating task.
> 
> Reported-by: Jan Stancek <jstancek@...hat.com>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: <stable@...nel.org> # 3.12+

Acked-by: Rik van Riel <riel@...hat.com>

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